The invention relates to a wiper arm with a pivotably connected wiper blade as generically defined by the preamble to claim 1.
Known windshield wipers have a wiper arm, which is comprised of a mounting part and a joint part pivotably connected to it, which has a wiper rod. The wiper arm is pivotably connected to a wiper blade, which is comprised of a supporting bracket system with a center bracket, and possibly secondary brackets, e.g. an intermediate bracket and/or claw brackets that hold a wiper strip. The brackets are also pivotably connected to the secondary brackets, allowing the wiper strip to adapt to the windshield curvature during the pivoting motion. The joints between the brackets are typically plastic parts, which simultaneously cover the end face of the profile of the primary bracket.
In addition, DE A1 197 38 232 has disclosed a wiper strip support element made of an elastic, high-strength plastic, which when unstressed, has a curvature designed to produce a uniform contact pressure when the wiper strip rests completely against the windshield during operation of the wiper blade. Plastic end caps are mounted on the end faces of the profile. Similar wiper blades with a support element made of spring steel have also been disclosed.
Large velocity differences between the inner region oriented toward the drive unit and the outer region of the wiper blade as well as stick-slip effects cause the wiper blade to vibrate. Particularly in the inner circle of the wiper blade where friction velocity is especially low, this leads to undesirable lateral movements, which starting from a certain magnitude, can cause the wiper blade to strike against the wiper arm and create a clattering noise. This is particularly critical when the windshield is dirty, iced over, not wet enough, or covered by snow. Since the wiper blade can thus temporarily lose contact with the windshield, the wiping pattern is also unsatisfactory. The wiper blade tends to rattle more the longer it is and the more bracket parts it contains. Furthermore, lightweight wiper blades with a low spring rigidity perform less favorably than others.
DE 37 44 237 A1 has also disclosed a windshield wiper, which, between a wiper arm and a claw bracket, has a device designed to guide a wiper blade, which is disposed at the end of the wiper blade oriented toward a drive shaft. The device is attached to the wiper arm and guides the wiper blade by means of at least one guide cheek in the vicinity of a joint between a center bracket and a claw bracket. Accordingly, the cheeks have to be long enough to reliably guide the wiper blade in all positions. Depending on the curvature of the windshield and the kinematics of the windshield wiper, there is the danger that long cheeks will collide with the vehicle windshield in certain positions. Finding a compromise is difficult if the windshield wipers are supposed to fit different vehicle windshields with very different curvatures.
DE 197 31 683 A1 has also disclosed a device for guiding a wiper blade, which is comprised of a first and second part. This device is disposed in the vicinity of the linkage point of the claw bracket and permanently connected to the joint part of the wiper arm, e.g. by means of gluing, welding, soldering, clipping, clamping, etc. The first part of the device has guide cheeks that encompass the joint position of the claw bracket and guide it in relation to the wiper arm. The second part also has guide cheeks between which the first part is guided in telescoping fashion so that its guide cheeks can be kept short and there is no danger of a collision with the windshield, even with sharp vehicle windshield curvatures. The first part is suitably connected to the device in captive fashion, e.g. by means of a flexible element.
The second part can also consist of a flexible tongue, which connects the first part to the device in such a way that the first part is rigidly guided in the movement direction of the windshield wiper, whereas it can flex in relation to the wiper arm, perpendicular to the windshield. Naturally, it is also possible to top for a combination of a flexible tongue and guide checks for the second part, in which the flexible tongue performs the function of the flexible element. It is also possible for the device to be made and assembled of sheet metal parts, but it is preferably an injection molded part made of a suitable plastic. But in any case, additional components are required for guiding the wiper blade, which results in increased manufacturing and assembly costs and additional raw material cost.
According to the invention, the second part of the device associated with the wiper blade is permanently connected to the wiper blade. The first part of the device associated with the wiper arm can also be permanently connected to the wiper arm; the necessary relative motion between the wiper arm and the wiper blade can be absorbed relatively freely by the flexible link so that the device does not change either the contact force of the wiper blade or its angle in relation to the vehicle windshield.
The first part of the device can also rest against the wiper arm with guide surfaces, which allow the wiper arm to move in the longitudinal direction and perpendicular to the windshield, but guide the wiper blade laterally, crosswise to the wiping motion so that the device does not apply any force to the wiper blade other than the lateral guidance. Since the guide surfaces are disposed on the side of the device oriented away from the vehicle windshield and since the part of the device oriented toward the windshield is mounted to the wiper blade, this prevents any collision with the vehicle windshield. The lateral guidance of the wiper blade limits lateral movements of the wiper blade and prevents the wiper blade from rattling or clattering. The guide surfaces are suitably provided with ribs extending in the stroke direction. This decreases the contact surface area, which reduces friction and prevents the guide mechanism from jamming.
The device is preferably embodied as a plastic component and, according to one embodiment of the invention, the part permanently connected to the wiper blade is formed onto a plastic end piece in the joint region of a bracket or wiper strip. Consequently, a separate part is not required for guiding the wiper blade. In addition, the end piece in the form of a cap or a bearing part is mounted along with the device in a single work step, which renders additional assembly steps unnecessary and keeps manufacturing cost down. This part is connected to a first part of the device by means of a link, which has one or more guide surfaces. The guide surfaces rest laterally against the wiper arm or engage in a guide profile of the wiper arm, e.g. a slot.
In a suitable fashion, the link is embodied as a flexible element, e.g. as a leaf spring, so that vertical motions between the wiper blade and the wiper arm, which are generated by the kinematic sequence during wiper operation, are compensated for. The spring force of the leaf spring is chosen so as to have no effect on the contact force of the wiper blade, in order to obtain an optimal wiper performance and to prevent excess wear and tear on the wiper rubber. With an appropriate design of the leaf spring, the first part, which is associated with the wiper arm, can be permanently connected to the wiper arm. This design can be considered whenever the relative motions between the wiper blade and the wiper arm in the longitudinal direction and/or in the direction perpendicular to the windshield are not very great.
The wiper blade guide device according to the invention solves the problems mentioned in the Prior Art section simply and without the use of additional components, so that no further assembly costs are incurred. Another advantage of this wiper blade guidance lies in the fact that the device is largely covered by the wiper arm, does not take up additional installation space, and allows for a compact design of the windshield wiper in the vicinity of the wiper arm and wiper blade. A compact windshield wiper generates less wind noise and has a better design.
To improve the lateral guidance of the wiper blade, according to one embodiment of the invention, the wiper arm has projections in the vicinity of the guide surfaces, which projections are oriented in the stroke direction of the vertical motion. The projections can have different profiles as needed, permitting various magnitudes of lateral force to be absorbed and different space requirements to be accommodated. Moreover, a form-fitting connection additionally improves the guidance.
The wiper blade guidance according to the invention is also suitable for very flat wiper blades, such as jointless types of wiper blades. In this case, the second part is embodied as an end cap, which embraces the wiper strip and the support element at the end and is permanently connected to them. Depending on the intended use, the leaf spring can be disposed on the top, on the side, or in the extension of the wiper blade, which permits a range of applications to be covered and various spring properties and support moments to be produced.